Solid state circuit interrupter



March 30, 1965 J. J. TIEMANN SOLID STATE CIRCUIT INTERRUPTER Filed March 24. 1960 Fig. 2.

{IF Fig. 4.

Fig. 3.

Voltage lnvenfor Jerome J 77em0nn,

Ms A Horn e y United States Pat n r 3,176,149 SOLID STATE CIRCUIT INTERRUPTER Jerome J. Tiemaun, Burnt Hills, N .Y., assignor to General Electric Company, acorporation of New York FiledMar. 24, 1960, Set. No. 17,432

15 Claims. ((31. 307-885) This invention relates to circuit arrangements which include semiconductor elements" and,' more particularly, to such arrangements in which the semiconductor elements are capable of operation in both high and low impedance conditions soas to provide s'witohing or circuit interrupting functions.

V In the operation of many electrical systems there is need for a small and reliable circuit arrangement which can be changed quickly and automatically from a low impedance condition, whereby a large current may flow,

to a high impedance conditiomwhich limits the current to a very small value without employing mechanical contacts or other moving parts. The semiconductor devices used in the practice of this invention are of two different negativeresistance types called current-controlled and voltage-controlled negative resistance devices. The typeof negativeresistance device is determined with respect to the ordinate which intercepts its current-voltage characteristic at only one point. sistance semiconductor devices are: controlled rectifiers, PNPN diodes andnnijunction and avalanche transistors all of which are now well-known in the art. Some of 3,176,149 Patented Mar. 30, 1965 sistance region appears varies depending upon the semiconductive material from which the device is fabricated. For example, the range of the negative resistance region is from about 0.04 to 0.3 volt for germanium; about 0.08

to 0.4;volt for silicon, about 0.03 to 0.3 volt for gallium antimonide, and about .15 to .6 volt for gallium arsenide.

For further details concerning the narrow junction .degenerate semiconductor device utilized in the practice of this invention reference may be had to my copending application Serial No. 858,995, filed December ll, 1959,

now abandoned, which is'assigned to the assignee of the present invention and incorporated herein by reference. The aforementioned. application has been abandoned in favor of a continuation-in-part application, Serial No. 74,815, filed September 9, 1960, which discloses and claims the subject matter of the parent application.

Circuit arrangements are known employing semi-conductor devices in combination with control voltage sources Examples of current controlled negative rethese devices, such as P-N-P-N diodes and controlled,

rectifiers, for example, comprise a semiconductive body to provide switching between two extreme impedance conditions. A typical circuit arrangement utilizes a PNPN diode and a suitable voltage source capable of producing both positive and negative output pulses to switch the PNPN device on and on, in addition to an accompanying sensing means to excite the control voltage source to produce a pulse of appropriate polarity to cause the semiconductor device to switch to its different impedance conditions. This pulse source and sensin means contributes to the complexity of the complete circuit interrupter arrangement and requires a variety of components. V p 7 I It is an object of thisinvention, therefore, to provide a new and improved solid state circuit interrupter arrangehaving four zones, contiguous zones being of opposite conductivity type and defining at least three P-N'junctions. Electrodes may be provided to the two end zones or to the two end zones and one of the intermediate zones. Current controlled negative resistance devices may also be provided by appropriate cascading of transistors. A

further description of semiconductor devices of the above range of their cur-v Inent which avoidsone or-rnore of the above disadvan tages.

Devices of this type are fabricated so ast-o provide regions of P- and N-type conductivity having a very nar-' row junction therebetween. Bothof the regions of the device are degenerate. The use of the term degenerate refers to a body or region of semiconductive material which, if N-type, contains a sufiicient concentration of excess donor impurity to raise the Fermi-level thereof to a value of energy higher than the minimum energy'of the conduction band on the energy band diagram for the semiconductive material. a P-type semiconductive body or regions degeneracyrneans that a sufiicient concentration of excess acceptor impurities are present therein to depress the Fermi-level to an energy lower than the maximum energy of the valence band on the energy band diagram for the semiconductive material. The Fermilevel in such an energy band diagram is the energy level at which the probability of there being an electron present is equal to one-half.

The forward voltage range wherein the negative re- Itisanother object of this invention to provide a circuit arrangement which automatically switches from a low impedance, condition to a high impedance condition whenever a predetermined current level has been exceeded.

It is an object of this invention to provide a new and improved circuit interrupter which combines simplicity and economy of components.

I It is still another object of this invention to. provide a current-threshold circuit interrupter which is suitable for large power requirements and makes possible a high degree of miniaturization.

Briefly stated, in accordance with one aspect of this invention, a solid state circuit interrupter comprises a narrow junction degenerate semiconductor .diode, hereafter referred to asa narrow junction diode, and a multilayer semiconductor'device connected in series with a circuit to be interrupted. The multilayer device and narrow junction diode both have high and low impedance conditions of operation. Means are provided to initiate current in the circuit by setting the diode and multilayer device to their low impedance conditions. Means are further provided which are responsive to the condition of the narrow junction diode to impress a voltage across T 1 its low to its high impedance condition. junction diode is caused to change from its-low to its high the multilayer device of a polarity and'duration'sufiicient to allow the device to recover to its high impedance condition whenever the narrow junction diode changes from The narrow impedance condition whenever the current in the circuit to be interrupted exceeds a predetermined value.

The novel features which I beleive to be characteristic 7 of my invention are set forth withparticularity in the ap pended claims. My invention itself, however, together with further objects and advantages thereof will best be understood by reference to the following description taken in conjunction with the accompanying drawings of this invention, 7 o r e e H v ,FIG. 4 is a typical current-voltage characteristic of a narrow junction degenerate semiconductor jdiodei such as used inthis inventionf t v bediments of this invention.

prbviddt' v I, I V 1 V. I It is a characteristic of the multi ayer semiconductor "devices ps'ed in this invention that they remain in ahigh impedance} condition "until a" critical breakdown voltage I, has; beenfexceede'df When this voltage is exceeded, how- V :ever, the device switchcs .to alowirnpedancelor highicoi I ductionstate andremains in this 'stateiffsufiicientvoltage 'is ,rnaintained across its terminals to insure the flow of ajQ 1 wherein like numeralsdes'ignat'e like vcomponents and in which: 1 V t 7' i FIG, 1 is a'schematic V the circuit interrupter'of this invention, I, a FIG-'2 is] a schematic diagram of an' ernbodiinent utilizing a' controlledrectifier as the particular multilayer-semiconductor device showing means for switching diagram of one the device to its high conduction jstate,

FIG. 3 is 'a typical current-voltagecharacteristic a "current-controlled negative vresistance a multilayer semiconductor'device suchas may be utilized in thepractice FIG. 5,is a graphical representation of the current invention, and

a rosource of voltage pulsesfi Semiconductor devices 1 embodiment of: r 1

rectifier,; as describediabove, is

semiconductor device, however, it iscau'sed to switch vto .itshigh conduction state in; a dilferentmanner. A controlled rectifier has, in addition to the electrodes conftacting the'twoendzones as-in the PNPN diode, an eleclikewise a multilayer trode conta'ctingone of thet-f'inte 'rrnediate zones. These voltage characteritsics of the two semiconductor devices utilized in the practice of thisiinventiori'illustrating.the" operating points" for the circuit arrangement "of this ion] degenerate semicon ductor diodel andia multilayersemiconductor device 2 f' connected in series with a voltage supply; 3, a utilization ymefans, representedschematically by resistance, 4 and a control voltage r source 5. Source 5. may beany era-i I ',plurality of means efiective to switch semiconductor. device; to its low impedance state, sii'chfas, for example;

and 2are connectedwith respcctto each other to provide that theforward current'is in the same direction. "For example, for one polaritythe 'N-type. conductivityregion of narrow junction diodefl is connected to the end P-type f conductivity region of, multilayer semiconductcir .d'evicef 2 while for the other polarity the-"P -type conductivity [region o ffnarrow junction diode l 'is connected'to the endpN-type conductivityregion of the -rnultila yer semiconductor. device 2. Foreither'polarity condition, therefore, narrow junction 'diode 1 and multilayer device 2 providealte'rnate regions foflopposite, conductivity type. .1 Means are provided which are responsiveto'the voltage acrossdiode 1' for impressing a voltage across thernultilayerdevice Z offl a polarity and duration sufiicient to allow device 2 to recoverito' its high impedance ,condi tionf 'This ma'y be by means of capacitancel connected FIGS; 6 and 7 are. schematic diagrarns 'o ffurther emelectrically in series witha i trolled rectifier 7 includesanf'anode electrodes, a cathode electrode 9 anda gateelcictrode Again, as in'FlG. l

' capacitance; 6- "shunts thc ser'ies-connectedsemiconductor devicesl'ahd 7 arid'this parallel'combination isconnected inseries with a circuit, to be interrupted. The circuit to supply'B, and resistancefl e triggered toits'high conductionf'stafegto initiate current 35 from currcnt source'11tcausing' thefdevice'to switch to electrodes, are called herein the anode electrode, "cathode electrode andgate electrode r espectively.- Such a con:

trolled rectifier is triggered to its high conduction state by, applyinga; current to the gatel electrode {causing the a controlled rectifier to switch toits high conduction state even th'ough' the voltagetacrossjthe device is less than the critical breakdown voltage,

v Forjincreasing' values of gate electrode currents, the.

device in the arrangement of FIG. I1Q a. V

In the circuitjnterrupter ar'rarigernentoi FIG; 2, therefore, there is shown narrow 'u'riction diode lconnected ntrolled rectifier 7. Conbe' interrupted is represented,schematically by voltage l'lheIcontrolledrectifier 7 is in' the" circuit, by supplyingcurrent to gate electrode 10 its high conduction state;

lf-the current through the multilayer device "in either 7 fofthe arrangements or EIG.- l 'orf2. is reduced to a value less" than that of the 'minirnumholdingcurrent or the voltage thereacross is'redu'ced to a;value 1ess' than that "required tosustain such-holding current, the multilayer device; returns to its high" impedance state and remains there until'bre'akdown is again initiatedjand the multiin parallel :with the series-connected diodefandmulti- 3- layer device The push-buttonzsjisnot essentialito the V operation ofthecircuitand is shownmerely'asone con- 'venientmeans of momentarily byflpass ing' the discharg'e current from capacitance fi which might tend to switch' T diode 13:0 its high;v impedance condition "when current is 'initiatedin the" circuit, ,Thefabove fare allthe compo nents required for this newllandf'improvedsolid state circuit"interrupting;arrangement,f ,No separate power supply 'is' required since the ,1 w power consumed is layer device is'caused toiswitch to its low impedance or high'conductionvstate'. 'The brealtdown voltag'e V sus tainirig voltage V; and minimum value of holding current V 13 are shown particularly f on ,the current vcltage' characteristic' for i'a typical multilayer{semiconductor device drawrr fromthe current to be,"interrupted; Thus, an

extremely simpler and; compact ,c' curt "nter'rupter; is

minimum amount'of current called its holding current.

inFIG. 3. t i t The current-voltage characteristic of, atypical narrow -junction"'de'generate semiconductordiode is "shown in a 1 16.14. The voltages-at whichlthe peak current li and f the -;valley currentl occur d fine-u on" the particular degenerate semiconductor device is fabricated; The mag .nitude of these currents, ihowevenfdepends; upon such semiconductive material from which the narrow junction factors la s the' junctionarea, 'bulkfre sistance of the semiconductive material and yario'u's'. other idetails I and techniqu'es of fabrication. It -is possible,:ftherefore," to obtain such devices with many' diiferentjvalucs of peakand valley [current For purposes of ii this inverition the. particular f'narrow junction 'diodeutili zed' musfhave 'a v'alleypurrent less than the minimum holding current of; the multilayer semiconductor device used'in combination: with'it, The

' narrow junctionldiode issele'cted', addition, tohave a peak current corresponding't'o'the threshold level above The voltage necessary tol sustairnthis current isfcalled the sustainingvoltage-and is very small asf compared to i the critical breakdown voltage,being usually on the order 'of one was: le ss,ydepe nding upon, the exact semiconductor devices utilized. i

In'FIG. 2 there is shown a circuit'interrupter inaccord ance with this invention employing a controlled rectifier r as the particular multilayer device. I The controlled":

which 'it is'desired toprovide automatic circuit interruptionf a v f I Y Since both the circuit arrangements shown iii'rros' 1' and 2 have substantially the sam e'modeiof operation, the following description has reference primarily "to the circuit arrangement of'FIG, 1.; In the "operation of the circuitarrangernentsshown in PEG-3.: 1 and 2 current is f established in the circuit-by causing the multilayer device to beswitched to itslow'impedance. or high conduction state. This may be provided,,for such devices as the PNPN diode and unijunction and avalanche transistors, by meansof-a voltage pulse such as, for example, from control source 5. This provides that the net voltage across the device exceeds the critical breakovervoltage causing breakdown of the junction and switching of the device to its high conduction state. Alternativelygsuch switching may be provided bymeans of an external voltage pulse either superimposed on the supply voltageor impressed directly across the multilayer device. This switching may also be provided, when utilizing a: controlledrectifier such as shown in FIG. 2, by supplying current to the gate elec trode" from current source l lcausing the device to switch to its high conduction state at avoltage less than its critical breakdown voltage.

"Means are provided which are responsive to thevoltage condition of narrow junction diode 1 for impressing a voltage across the multilayer device 2 which reduces the net voltage across its terminals to a value less than the voltage required to sustain the multilayer device in its high conduction state. Thecircuit arrangement illustrated in FIG. 1 comprises a capacitance 6 in parallel with the series connected-narrow junction diode-1 and multilayer device 2. Since capacitance 6 isin'parallel with the series combination of semiconductor devices 1 and 2 the voltage is the same across both branches. For

convenience of description, these branches are referred to herein as the capacitance and semiconductor branches, respectively. r

The current in the semiconductor branch establishes a.

loadline for narrow junction diode. 1 such as shown in FIG, 5 at D. This load line intersects the narrow junction diode current-voltage characteristic in a region of low positive resistance'shown at 12 and a region of high positive resistance shown at 13-. .Since both these intersections are in regions of positiveresistanc'e, the load line D provides narrow junetion diode 1 with two stable conditions of operation. Because of the nature of the nega tive resistance region of thecharacteristic, for a loadline such as that shown at D, there can be no stable operation in the negative resistance region and the only conditions of operation are at the low and high impedance conditions 12 and 13 respectively.

Current is established in the circuit to be interrupted by setting multilayer device 2 and narrow junction diode 1 to their low impedance conditions, as described above,

and is maintained until interrupted. Diode 1 is selected to have a value of peak current corresponding to a value above which it is desired to provide automatic ,circuit interruption. As long as the. current in the circuit to be interrupted remains at a value less than the peak current of diode 1, the semiconductor branch remains in a low impedance condition and this amount of current is carried by the series connected semiconductor devices 1 and 2. Since semiconductor devices land 2 are inseries, they each carry the total current of the semiconductor branch at all times. The current in diode 1 for the operat-.

ing point 12 and in'multilayer device 2 for point 14 is shown as I on the curves of FIG. 5.. When the current in the circuit to' be interrupted reaches a value which would result in a narrow junction diode current in excess of the diodes peak current, the diode abruptly switches to its other stable operating condition 13 reducing the "current in the semiconductor branch to a value less than the minimum holding current 13 of the multilayer device 2. If the current is held at this value for a short period of time, the multilayer device recovers to itshigh impedance condition, effectively interrupting the current in the circuit. In the circuit arrangements shown in FIGS. land 2 the voltage across multilayer device 2 is reduced to a value belowthat corresponding to its sustaining voltage and held at this voltage for a short period of time by capacitance 6.

proximately 0.7 volt. There is a change in voltage when narrow junction diode 1 switches from its low impedance condition at point 12 to its higher impedance condition at point 13 of 0.62 volt. For a particular multilayer device 2 for this same example the sustaining voltage V may be approximately 0.7 volt. and the voltage corresponding to point 14 approximately 1.0 volt. Thus a voltage change in excess of 0.3 volt will reduce the voltage across the multilayer device 2 below its minimum sustaining voltage. The voltage change of 0.62 volt across narrow junction diode 1, therefore, is sufiicient to decrease the voltage across multilayer device 2 to a value below its sustaining voltage V v t a r Since the voltage across capacitance 6 cannot change instantaneously the voltage across the semiconductor branch tends to remain constant when narrow junction diode 1 is caused to switch from its lowimpedance condition to its higher impedance condition. The voltage across the multilayer device, therefore, must decrease by an amount equal in magnitude to the increase in voltage across narrow a junction diode 1-. Multilayer device 2 is so selected, therethe change of condition of narrow junction diode 1. Thus,

the voltage across multilayer device 2 is reduced to a value less than the sustaining voltage V necessary to maintain the multilayer device in its high conduction state. This condition persists during the time capacitance 6 is being charged in response to the increased voltage across narrow junction diode 1 Capacitance 6 is selected to have a charging time sufiicient to allow multilayer device 2 to recover to its high impedance condition Where it remains and the current in the circuit is effectively interrupted.

, The time required to allow multilayer device 2 to recover to its high impedance condition is very short and the circuit interrupter arrangement of this invention is capable of extremely high speed operation. For example,

for atypical silicon controlled rectifier, the time the rec- 15 and capacitance 16 in series combination acro'ss multilayer device 2. Multilayer device 2 is connected in series with a current-threshold sensing circuitarrangement which includes diode 1 and resistance -17 conn'ected in parallel relationship by inductance 18. When sucha parallel combination is connected in series with a circuit to be interrupted, a voltage pulse is developed through inductance 18 whenever the operating condition of diode 1 is changed.

For further details of such a current'threshold sensing .circuit arrangement, reference may be had to my copending application, Serial No. 863,142, filed December 31,

1959, and assigned to the assignee of the present invention.

The voltage pulse from the sensing circuit arrangement isimpressed across the multilayer device 2 through in ductance 15 and capacitance 16 to allow the multilayer ,device to recover to its high impedance condition. Again,

the charging time of capacitance 16 must be long enough to allow such recovery. If, however, the voltage of the voltage source or,-convenie n circuit tobe interrupted; g V I t diode 11is initslow impedance condition only a small voltage is impressed: between the base'and emitter electrodes 23 and 24 respectivelyand sub? stantiallyt no injection'occursat the emitter base junction I L "of-transistor'il," There is only a'very sniallcurrent in the hase-coileetor circuit"andtransistorfl, therefore, is substantially non-conducting; There 'is also only a very small currentin'r esistance 26am a smallvolta'gediiference appearingl thereacross. When narrow junctiondiode '1 is caused to switch to itshigh impedance condition, however,

vetfectively interrupting the 'circuit 7 this invention.

as by a transformer, for example, a smallervalue of In FIG. 7, means for utilizing the voltage across narrow junction diode]; to allow recovery of multilayerdevice 2 to its high impedance condition is shown as transistorgl and capacitance ZZnTransisto'rfl for example, may be t of 'N -P+N-typeihaving base elect'rode23, emitter electrode 7 j 24 and collectonelectrode 25. "Transistor 2 lis connected t in circuit withsna'rrow junctiondiode l su'ch'that transistor l is in a nonconducting state when narrow junction diod'e'l is in itsdow' impedance condition and in ac onductmg state t 'when narrow junction'diode 1 isin its highimpedance-condition j For example,"transistor. 2}; may have base electrode'23 connected to one terminal of narrow. junction.

diode l =and emitter electrode-24 connected to-the other a terminal thereof, The voltage appearingl'across' narrow junction diode 1 isthus impressed between thehase'and 'emitt'eielectrodes of transistor ;Collector 25 may be s connected througha suitableimpedance such'as resistance 26 to ajvoltag'e source of positive polarity and magnitude i1 largecompared to the forward voltage difierence appearing across the multilayer device 2. .This maybea separate t When'narow junctiona large current is diverted to the emitter-electrode 24 and t transistor El ise-rendered conducting. This causes a-large' current in the collectorcircuit and in resistance'ld. Be- I cause of the current in resistance 26 a large voltage difference appears across its terminals. jCapacitanceZZ begins to charge] to'this increased, voltage and by this action the I voltage across multilayerdevice 2 is driven; negative.v

'Again, the charging time of capacitancezlis selected so that thevoltageacrossmultilayer device Z- is held below ;the' minimum sustaining voltageVgfor a time sufiicientto allowfth'e multilayer device 2 to-recoverito' its'high impedance condition; This apparenfltherefore, thatthisarj rangementisresponsive to thevolt agecondition'of narrow junction diode 1 andis effective to maintain the voltage across; multilayer device? at avaluejbelow. the minimum sustaining- Voltage and al 7 pedance'condition. v a l l l v t This invention oifers circuit simplicity and economyof components. When the-predetermined current value is exceeded-there 'isanjinstantaneous large magnitude voltage changejatdiode 1 which is utilized to allow themulti- 7 laycrdevice to recover-to its; 7

low recovery; to the high iinhigh impedance condition,

invention have beeirshown by wayor illustration, fmany modifications and ch arigeswill occur to thoseskilledin' the art. It thereforerto be understood that the'ap pe'n'ded claims are intended-to cover all such modifications hin thetrueispirit and-scope of." l

and changes "as jfall wit What; I] claim 1. 'A solid state circuit interru tly, thep'ositive terminal oft-the H v pt er comprising: ya nar-t ro\ v unction degenerate semiconductor diode; a multilayeriserniconductor deyicesaid diode-and' multilayer and means'responsive to the voltage across said diode for impressing a voltage aoross saidimultilayerdevice of po- :nnry and duration sufficientto allow said multilayer device to'recover to itshigh impedance condition whenever said diode is'c'aused to change from its low to its 1 high impedanceconditioninresponsej to an increase in current'throughsaid diode in excess of the value of its Q peak current, I V 2. The solid state ci .15 in the multilayer semiconductor device is :a controlled rectifier; 1

f A'circuit interrup te'r comprisingi [a narrow junction sist-ance region in therorward low voltage: range of its 30 current-voltage characteristima multilayer semiconductor device exhibiting ahigh irnpedance, condition under a minimum holding current value and allow impedance tcondition above said holding currentrmeans connecting saidjdiode and multilayer device inseries witha circuit diode for operation in itsgfllow impedance, condition; and I 'means responsive to the conditioniof said diode for main- 4 taining a voltage across,said multilayer-device which is allow'said multilayer device to recover to its high impedance condition inv response wan" increase in "current throughsaid diod V currents:

' l "6. The'so in the multilayer device is a controlled rectifier.

- 7. The 'soiid state circuit interrupter of claim 5 wherein the 'means responsiveito theiccndition of said diode for 'maintaining avoltage less. than the multilayer device sustainingvoltage is' 'a capacitance shunting :the series confi'nected diodeand multilayer device;, 7 V i 8 The solid state circuit interrupter of gthan its sustaining" volt pacitane T I 9 A solid'state circuit interrupter comprising: a narrow junction degenerate semiconductor'diode having pre- 6 determined peak and valleycuri'ent valuesiand avoltage controlled negative resistance re'gion' inth e forward low (voltage rangeof its current-voltage characteristic; a multilayer semiconductor device eighibitin'g current-controlled ageincludes a transistor and caglteristicf'said device furtherfexhihi'tiiigia high impedance a low impedance'at current values above said holding ourdition of said-diode for impressing; a ,voltagepulse'of 75 polarity and duration'suificient to allow'said multilayer rcuitinterrupter offclairn 1 where- {degenerate semiconductor diode; Va 'mult'ilaye'r se micon- V determined peak and valley,currentsf'andia negative re- 35 to be interrupted; means in circuit With'sa'id multilayer device for setting it I to fit's' lowfinipedance' condition to initiate current in said" circuit, said current biasing said less than its'sustaining voltage fora time sufiicient toe in excessofjjthe valuejof its peak 7 lid state circuit interrupter of claim 5 wherea 7 claim 5 wherel in the means responsive to'thecfondition of said diode'for i maintaininga voltage across the multilayer device less negative res-istance region in its current volt age ch'arac- ,aticurrent values jbelowsa minimurn holding current and rent;v means'conneeting said diode andinultilayer device" i in serieswith a circuit to be" interrupted providing stable 7 l 7 V f V; l high and low impedanceroperating'conditions therefor, as new and des.ire"to;secure by Letters Patentof'theUnitedStatesiszt 9 device to recover to its high impedance condition whenever the current in the circuit to be interrupted exceeds a predetermined value causing said diode to switch to its high impedance condition.

10. A solid state circuit interrupter comprising: a narrow junction degenerate semiconductor diode exhibiting a voltage controlled negative resistance current-voltage characteristic; a multilayer semiconductor device exhibiting a current controlled negative resistance current-voltage characteristic; said narrow junction diode andsaid multilayer device connected in series; a capacitance shunting said series connected narrow junction diode and multilayer device forming a parallel combination; means connecting said parallel combination in series with a circuit to be interrupted; and means in circuit with said multilayer device for setting said multilayer device to its low impedance condition to initiate current in said circuit.

11. A solid state circuit interrupter comprising: a narrow junction degenerate semiconductor diode exhibiting a voltage-controlled negative resistance current-voltage characteristic; a multilayer semiconductor device exhibiting a current-controlled negative resistance current-voltage characteristic, said multilayer device having a high impedance at current values below a minimum holding current and a low impedance at current values above said minimum holding current; means connecting said diode and said multilayer device in series with a circuit to be interrupted and establishing a direct current load line providing two stable operating conditions for said narrow junction diode, one of said conditions corresponding to a low impedance condition and providing a current greater than said holding current and the other condition corresponding to a high impedance condition and providing a current less than said holding current; means setting said diode and multilayer device to their low impedance controlled negative resistance device and a voltage-controlled negative resistance device, each of said devices having a low impedance and a high impedance stable operating condition; means adapted to connect each of said devices in series in a circuit to be interrupted, both of said devices being connected to be forward biased; and means connected to said current-controlled device: adapted to reduce the forward breakdown voltage thereof to initiate conduction in said circuit.

13. A circuit interrupter comprising: a current-con- 10 condition in the forward current direction, said currentcontrolled device exhibiting a minimum value of holding current below which switching from its low impedance condition to its high impedance condition occurs; a

voltage-controlled semiconductor negative resistance device having a low impedance and a high impedance stable operating condition in the forward current direction, said voltage-controlled device exhibiting a peak current value above which switching from its low impedance condition to its high impedance condition occurs; means adapted to connect said devices in series in a circuit to be interrupted when the magnitude of current therein in the forward direction through said devices exceeds said peak current value, said devices being connected with respect to each other to provide that their respective forward currents are in the same circuit direction; and means connected to said current-controlled device adapted to reduce the forward breakdown voltage thereof so that conduction is initiated in said circuit.

14. A solid state circuit interrupter comprising: a tunnel diode having an anode and a cathode; a controlled rectifier having an anode, a cathode and a gate electrode; means connecting the cathode of said tunnel diode to the anode of said controlled rectifier; means connected to the anode of said tunnel diode and the cathode of said controlled rectifier adapted to connect said tunnel diode and said controlled rectifier in series with a circuit to be interrupted upon occurrence of a forward current through said tunnel diode in excess of the peak current thereof; and, means connected to said gate electrode adapted to initiate conduction in said controlled rectifier.

15 A solid state circuit interrupter comprising: a tunnel diode voltage-controlled negative resistance device; a controlled rectifier current-controlled negative resistance device having a gate electrode; a source of unidirectional voltage; resistive utilization means; means connecting said tunnel diode, controlled rectifier, source and utilization means in series circuit relationship, said tunnel diode and said controlled rectifierreach being connected so that trolled semiconductor negative resistance device having a low impedance and a high impedance stable operating the current-therethrough is in the forward direction; and, means connected to said gate electrode adapted to switch said controlled rectifier from its high impedance to its low impedance state.

References Cited in the file of this patent UNITED STATES PATENTS 2,843,765 Aigrain July 15, 1958 2,877,359 Ross Mar. 10, 1959 2,909,705 Husson Oct. 20, 1959 2,920,240 Macklem Jan. 5, 1960 2,949,544 Hill et al. Aug. 16, 1960 3,040,191 Bright' June 19, 1962 3,040,194 Jones et al. June 19, 1962 3,040,195 Jones et al. June 19, 1962 3,040,270 Gutzwiller June 19, 1962 

1. A SOLID STATE CIRCUIT INTERRUPTER COMPRISING: A NARROW JUNCTION DEGENERATE SEMICONDUCTOR DIODE; A MULTILAYER SEMICONDUCTOR DEVICE, SAID DIODE AND MULTILAYER DEVICE EACH HAVING A LOW AND HIGH IMPEDANCE STABLE OPERATING CONDITION; MEANS CONNECTING SAID DIODE AND SAID MULTILAYER DEVICE IN SERIES WITH A CIRCUIT TO BE INTERRUPTED; MEANS FOR SETTING SAID DIODE AND MULTILAYER DEVICE IN THEIR LOW IMPEDANCE CONDITIONS TO INITIOATE CURRENT IN SAID CIRCUIT; AND MEANS RESPONSIVE TO THE VOLTAGE ACROSS SAID DIODE FOR IMPRESSING A VOLTAGE ACROSS SAID MULTILAYER DEVICE OF POLARITY AND DURATION SUFFICIENT TO ALLOW SAID MULTILAYER DEVICE TO RECOVER TO ITS HIGH IMPEDANCE CONDITION WHENEVER SAID DIODE IS CAUSED TO CHANGE FROM ITS LOWER TO ITS HIGH IMPEDANCE CONDITION IN RESPONSE TO AN INCREASE IN CURRENT THROUGH SAID DIODE IN EXCESS OF THE VALUE OF ITS PEAK CURRENT. 